Safety interlock mechanism for an electric switch and receptacle unit



Oct. 4,1966 R. M. BACON 3,277,253

SAFETY INTERLOCK MECHANISM FOR AN ELECTRIC SWITCH AND REGEPTACLE UNIT Filed May 25, 1964 2 Sheets-Sheet l INVENTOR.

T165 71w} Y Roaeer M Ema/v R. M. BACON SAFETY INTERLOCK MECHANISM FOR AN ELECTRIC Oct. 4, I966 SWITCH AND RECEPTACLE UNIT 2 Sheets-Sheet 2 Filed May 25, 1964 INVENTOR. B05527 M. BACON 7 dd/450M, SETTLE 226K410 HTTOEMEY5 United States Patent The present invention relates to the safety interlock mechanism for an electrical switch and receptacle unit, and more particularly to an interlock mechanism which prevents opening of the main access door or removal or I insertion of a plug when the switch is in the on position.

Switch and receptacle units to which the present invention is particularly adapted are of the type generally used in industry for supplying electrical power to high power devices such as portable welding machines.

As will be appreciated, the electrical power available at such units is lethal. It is highly desirable that workmen be unable to contact energized portions of the units when the switch is in the on position. It is conventional to provide an interlock structure for the main access door of such units to prevent opening of the main access 'door when the unit is energized. However, heretofore, structure has not been provided in such units to prevent insertion or withdrawal of a plug from the receptacle when the unit is energized. In accordance with the present invention, means are provided to lock the access opening to the receptacle when the unit is energized.

An object of the invention is to provide a switch and receptacle unit having an interlock to prevent access to the receptacle when the switch is in the on position.

Another object of the invention is to provide such an interlock system which cooperates with the interlock system provided in the unit for locking the main access door when the switch is in the on position.

A further object of the invention is to provide a door closing the access open-ing to the unit receptacle when there is no plug inserted into the receptacle.

A further object of the invention is to provide a sliding panel interiorly of the unit casing which partially blocks the access opening to the receptacle when the switch is in the on position to thereby prevent insertion of a plug.

A still further object of the invention is to provide latching means on the inner surface of the door for the receptacle access opening, the latching means interlocking with the sliding panel when the door is closed and the switch is in the on position.

An additional object of the invention is to utilize structure on the plug to cooperate with the sliding panel to lock the plug in place when the swtich is in the on position.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a view in perspective of one embodiment of the switch and receptacle unit of the present invention;

FIGURE 2 is a front view of the unit of FIGURE 1 with the main access door and the receptacle access door in open positions;

FIGURE 3 is a sectional view taken substantially along the line 33 of FIGURE 2 looking in the direction of the arrows but with the plug removed and the receptacle access door closed illustrating the condition of the interlock system when the switch is in the off position;

FIGURE 4 is a sectional view similar to FIGURE 3 but with the switch in the on position;

FIGURE 5 is a sectional view taken substantially along the line 5-5 of FIGURE 1 looking in the direction of the arrows with the switch in the off position;

FIGURE 6 is a view in perspective of a modified locking structure for the receptacle access door; and

FIGURE 7 is a cross-sectional view of the locking structure of FIGURE 6.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

The switch and receptacle unit 10 includes a casing 12 having a main access door 14 on the front wall 16 and a receptacle access door 18 on the bottom wall 20. The casing 12 is adapted to be mounted on a suitable support surface such as a wall.

As Will be noted in FIGURE 2, a receptacle 22 is mounted within the casing 12 adjacent to the bottom wall 20. The receptacle 22 is for S-phase AC. power and has three leads 24, 26, 28 extending therefrom into connection with the binding posts for three fuse holders 30, 32, 34. Fuses 36, 38, 40 are mounted in the fuse holders. Leads 42, 44, 46 extend from the fuse holders into a connector unit 48 from which extends a cable 50 which is ultimately connected to a source of power.

An on-otf switch 52 is provided to control the application of electrical power to the receptacle 22. The switch 52 includes a pivotal switch arm 54 mounted exteriorly of the casing 12 on the front wall 16. The switch arm 54, as shown in FIGURE 2, is pivoted to the o position and in FIGURE 1, the arm 54 is pivoted to the on position. As shown in FIGURES 2 and 5, the switch arm 54 is connected, by linkage 5 6, to a reciprocal element 58 which is positioned within the casing 12. One end 60 of a pivotal element 62 is pivotally connected to the reciprocal element 58. The pivotal element 62 is pivotally mounted intermediate its ends at 64 to a fixed support element 66. A slot is provided in the wall 68 of the support element 66 to permit pivoting of the element 62. The end 70 of element 62 is forked and receives a projection 72 of a switch element 74. The switch element 74 actuates the contacts (not shown) of the switch 52 to the open and closed positions. As shown in full lines in FIGURE 2, the pivotal element 62 has been pivoted to move the switch element 74 to a position wherein the switch contacts are open. As shown in dotted lines, the pivotal element 62 has been pivoted to position the switch element 74 to close the contacts of the switch 52.

An interlock system is provided to lock the main access door 14 in the closed position when the switch 52 is in the on position.

As will .be noted in FIGURE 2, a pair of elongated locking bars 76, 78 are provided on the inner surface of the main door 14. The inner ends of the locking bars are pivotally attached at 80, 82 to a pivotal disc 84, the disc 84 being pivotally attached by bolt 86 to the door 14. The outer ends 88, 90 of the locking bars 76, 78 extend through guides 92, 94. The disc 84 is spring urged to the position illustrated in full lines in FIGURE 2 wherein the outer ends 88, 90 of the bars 76, 78 are drawn inwardly.

A handle 96 is provided on the exterior of the door 14. The handle 96 is operatively connected to the disc 84 by the bolt 86. The handle 96, when moved to the position shown in FIGURE 1,. causes outward movement of the locking bars 76, 78 to the dotted line positions illustrated in FIGURE 2. When the locking bars are so extended and the door is. closed, the ends 88, 90 extend beneath the portions 98, 100 of the casing front wall 16 to lock the door in the closed position.

The door 14 is maintained in the locked position by means of a latching element 102. As will be noted in FIGURE 2, the latching element 102 is pivotally mounted by means of bolt 104 adjacent the disc 84. The latching element 102 has a tooth 106 which, when the disc 84 is pivoted in the counterclockwise position as viewed in FIGURE 2, will engage a notch 108 provided in the disc 84 to thus maintain the disc 84 in a position where in the locking bars 76, 78 are extended. The latching element 102 is urged into the locking position by means of a spring 110. The bolt 104 has a slotted head 112 which is accessible exteriorly of the door 14. The latching element 102 may be pivoted out of engagement with the disc 84 by applying a screwdriver to the head 112. However, means are provided to prevent such pivoting of the latching element 102 when the switch 52 is in the on position.

As will be noted in FIGURES 2 and 5, a cam-ming element 114 extends at approximately right angles from the latching element 102. The cam 114 is adapted to engage a pivotal locking element 116 when the switch 52 is in the on position. As shown in FIGURE 5, the locking element 116 is pivotally attached at 118' intermediate its ends to an elongated link 120. The link 120 is fixedly attached to the reciprocal element 58 which, as will be recalled, moves forwardly and rearwardly in response to actuation of the switch arm 54. The member 58 has a pin 122 which engages the locking element 116 and prevents pivoting thereof when the switch is in the on position and disengages this element to permit pivoting thereof when the switch is in the off position. As will be noted, the locking element 116 has a straight portion 124 which abuts against the pin 122 when the pin is in the position shown in full lines, this being the position of the pin when the switch is in the off position. A projection 126 extends from the locking element 116 towards the pin 122. When the pin 122 is in the position shown in dotted lines, which is the on position of the switch, the surface 128 of the projection 126 abuts against the pin 122 and prevents pivoting of the locking element 116 in the counterclockwise direction as viewed in FIG- URE 5.

A spring 130 is connected at one end to the locking element 116 and at the other end to a support bracket 132. The spring 130 biases the locking element 116 toward the pin 122. The cam 114 has a cam surface 134 which engages the edge 136 of the locking element 116. When the switch 52 is in the off position, the latching element 102 may be pivoted, with the cam surface 134 forcing the locking element 116 out of the way, to thus permit retraction. of the locking bars 76, 78 and opening of the door 14. However, when the switch 52 was in the on position, the latching element 102 cannot be pivoted because of the engagement of the locking element 116 with the pin 122. Thus, the locking bars 76, 78 cannot be retracted and the door 14 cannot be opened.

The link 120 also actuates the interlock system for the receptacle access door 18. As will be noted, this link extend-s forwardly to a point adjacent the bottom wall 20. The link 120 is pivotally attached to one leg 138 of an L-shaped link 140 at 142. The link 140 is pivotally attached to the back wall 144 of the casing 12 at 146, this being the juncture of the legs 138, 148. A pin 150 extends from the end of the leg 148 into a slot 152 provided in a projection 154 which extends from a slidable panel 156.

The panel 156 is mounted in guides 158, 160 for sliding across the face of the bottom wall 20. As will be noted in FIGURES 3 and 4, the panel 156 has an arcuate cut-out portion 162 adjacent the circular receptacle access opening 164.

The receptacle access door 18 has a pair of oifset tabs 166, 168 on the inner face 170. The tabs 166, 168 are spaced approximately 90 apart around the periphery of an imaginary circle. The tabs 166, 168 include legs 172, 174 which extend at right angles from the door face 170,

each leg 172, 174 having a tab portion 176, 178 extending therefrom towards the periphery of the access opening 164. A notch 180 is provided in the bottom wall 20 to permit passage of the tab 166. The tab 168 clears the opening 164 without the necessity of a notch.

As illustrated in FIGURE 3, when the switch 52 is in the off position, the panel 156 is moved away from the access opening 164. As will be noted in FIGURE 2, movement of the switch arm 54 to the off position moves the link towards the right as viewed in FIG- URE 2, causing pivoting of the link in the counterclockwise direction to thus slide the panel 156 away from the receptacle access opening 164. When the panel 156 is in this position, the door 18 may be opened and a plug 182 inserted through the opening 164 into connection with the receptacle 22.

FIGURE 4 illustrates the condition wherein the switch 52 is in the on position and no plug is connected to the receptacle 22. Referring to FIGURE 2, it will be noted that when the switch arm 54 is moved to the on position, the link 120 is moved to the left, causing the link 140 to pivot in clockwise direction and slide the panel 156 into engagement with the tabs 166, 168 provided on the access door 18. It will be appreciated that this door is thus locked in the closed position when the switch 52 is in the on position.

The plug 182 is provided with an annular projection 184. When the plug 182 is inserted int-o connection with the receptacle 22 and the switch 52 is closed, the arcuate portion 162 of the panel 156 partially surrounds the plug 182 and engages the projection 184, which is positioned interiorly thereof, to thus prevent withdrawal of the plug 182. It will be appreciated that instead of an annular projection 184, an annular recess could also be utilized for the reception of the arcuate portion 162 of the panel 156 to lock the plug in position when the switch 52 is closed.

It will thus be appreciated that the present invention provides, in a single interlock system, means for locking both the main door 14 and access door 18 or plug 182 in position when the switch 52 is closed. Conversely, each of these elements may be opened or removed, respectively, when the switch 52 is in the off position. Further, if the access door 18 is not closed when the switch 52 is closed, then the panel 156 will partially block the opening 164 and prevent insertion of a plug. It is thus virtually impossible for a workman to contact any of the electrically energized elements of the switch and receptacle units 10 when such elements are energized. It will be appreciated that this is an important safety factor and prevents injury to the workman as a result of his carelessness or lack of understanding of the dangers inherent in manipulating the switch unit 10 when the switch 52 is closed. It will also be understood that the invention may be applied to a switch unit having a plurality of receptacles and receptacle access doors.

An alternate locking structure for the receptacle access door 18 is illustrated in FIGURES 6 and 7. As will be noted, the tabs 168, 176 are eliminated. In place of the tabs, a hinge-type latching mechanism is provided on the panel 156 to cooperate with an inwardly projecting finger 192 provided on the door 18.

The locking mechanism 190 com-prises a hinge having leafs 194 and 196. The upper leaf 194 is secured to a small plate 198 as by welding and the plate 198 is secured in the same manner to the inner face of the panel 156 a short distance above the arcuate portion 162.

The lower leaf 196 forms a latching element. Leaf 196 is free to pivot and is normally positioned in front of a cutout 200 in the panel156. Thecutout 200 is slightly wider than the leaf 196. The leaf 196 is biased by a spring 202 to the position shown. A second small plate 204 is secured to the inner face of the leaf 196. The plate 204 is wider than cutout 200. The leaf 196 may thus be pivoted inwardly but is prevented from pivoting through the cutout 200 by abutment of the plate 204 against the panel 156.

The finger 192 on the door 18 is in alignment with the cut-out 200, whenthe panel 156 is moved to the position shown by closure of the switch 52. The cutout 200 is wider than the finger 192 thus permitting passage of the finger thereby. The door 18 is biased by a spring 206 to the closed position illustrated.

The finger 192 terminates in an upwardly angled portion 208. The portion 208 extends above the lower edge of the plate 204.

In operation, when the switch 52 is closed, the panel 156 is moved to the position as shown in FIGURES 6 and 7 as previously described. When the door 18 is released, it will swing to the closed position under the action of spring 206. The finger 192 will contact hinge leaf 196 and pivot the leaf 196 and plate 204 inwardly. As soon as the finger portion 208 has passed by the plate 204, the hinge spring 202 will bias the leaf 196 back towards the panel 156: The door 18 cannot then be opened because the finger portion 208 is engaged by the plate 204 which abuts against the panel 156. It will be noted that any force tending to open the door 18 is taken directly by the plate 204 thus avoiding any stress on the hinge spring 202.

The door 18 may, of course, be opened when the switch 52 is opened. As previously described, opening 'of switch 52 causes sliding of panel 156 out of its obstructing position.

The embodiment of FIGURES 6 and 7 is even more foolproof than the previously described receptacle access door locking mechanism. Whenever the door 18 is released and the switch 52 is closed, the finger 192 will engage the plate 204. In the embodiment of FIGURES 3 and 4, if the door 18is held open while the switch 52 is being closed, the tabs 166, 168 will not subsequently engage the panel 156.

Having thus described my invention, I claim:

1. In an electrical switch and receptacle unit, a casing, said casing having a main access doorand a receptacle access door, a receptacle within the casing, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, and an interlock structure operatively connected to the switch actuating member to lock the main access door closed and lock one of a plug connected to the receptacle and the closed receptacle access door in place when the switch actuating member is positioned to close the switch.

2. In an electrical switch and receptacle unit, a casing, said casing having a main access door and a receptacle access door, a receptacle within the casing, and a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, said casing including first latching structure to lock the main access door in the closed position, said casing including second latching structure to lock one of a plug connected to the receptacle and the closed receptacle access door in place, and linkage Within the casing operatively connected between the switch actuating member and the first and second latching structures to lock said latching structures in place when the switch actuating member is positioned to close the switch.

3. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, and an interlock structure within the casing operatively connected to the switch actuating member to look one of a plug connected to the receptacle and the closed receptacle access door in place when the switch actuating member is positioned to close the switch.

4. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a latching structure within the casing adjacent to the receptacle access opening, means on the interior of the casing adjacent to the receptacle access opening for engagement with said latching structure, a plug for connection with the receptacle, said plug having means for engagement with said latching structure, and linkage within the casing interconnecting the latching means and switch actuating member operative to move the latching structure into engagement with one of the closed receptacle access door and plug when the switch member is positioned to close the switch.

5. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, saidcasing having a receptacle access door for said opening, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a plug having locking structure thereon, said plug being receivable through the receptacle access opening and connectable to the receptacle with the locking structure of the plug positioned within the casing, said receptacle access door having locking structure on the interior face thereof, the locking structure of the receptacle access door being positioned within the casing when the door is closed, a movable latching member within the casing engageable with one of the locking structure of the plug and access door, and linkage within the casing between the latching member and switch actuating member to move the latching member to a position for engagement with one of the locking structure of the plug and access door upon movement of the switch actuating memher to close the switch.

6. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a plug having locking structure thereon, said plug being receivable through the receptacle access opening and connectable to the receptacle with the locking structure of the plug positioned within the casing, said receptacle access door having locking structure on the interior'face thereof, the locking structure of the receptacle access door being positioned within the casing when the door is closed, a movable latching member movable to a position for obstructing the receptacle access opening and for engagement with one of the locking structures of the plug and access door, and linkage within the casing between the latching member and switch actuating member to move the latching member, upon movement of the switch actuating member to close the switch, to a position for partially blocking the receptacle access opening and engagement with one of the locking structures of the plug and access door.

7. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a switch within the easing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a plug having locking structure thereon, said plug being receivable through the receptacle access opening and connectable to the receptacle with the locking structure of the plug positioned within the casing, said receptacle access door having locking structure on the interior face thereof, the locking structure of the receptacle access door being positioned within the casing when the door is closed, a latching plate slidably mounted within the casing, said latching plate being slidable to a position partially blocking the receptacle access opening, said latching plate having a recess on one edge thereof for engagement of the plate with one of the locking structures of the plug and access door, and linkage within the casing between the latching plate and switch actuating member to slide the latching plate to a position partially blocking the receptacle access opening for engagement with one of the locking structures of the plug and access door upon movement of the switch actuating member to close the switch.

8. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a plug having a projection on the exterior thereof, said plug being receivable through the receptacle access opening and connectable to the receptacle with said projection positioned within the casing, said receptacle access door having a tab structure on the interior face thereof, the tab structure of the receptacle access door being positioned within the casing when the door is closed, a latching plate slidably mounted within the casing engageable with one of the projection of the plug and access door tab structure, and linkage within the casing between the latching plate and actuating member to move the latching plate to a position for engagement with one of the projection on the plug and access door tab structure upon movement of the switch actuating member to close the switch.

9. In a switch and receptacle unit, a casing, said casing having a main access door, a receptacle within the casing, a switch within the casing having a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, said casing having a receptacle access opening, said casing having a receptacle access door for said opening, a plug having locking structure thereon, said plug being receivable through the receptacle access opening and connectable to the receptacle with the locking structure of the plug positioned within the casing, said receptacle access door having locking structure on the interior face thereof, the locking structure of the receptacle access door being positioned within the casing when the door is closed, a movable latching member within the casing engageable with one of the locking structure of the plug and access door, locking structure on the main access door to lock the main access door closed, and linkage within the casing operatively connected to the switch actuating member and having latching means associated therewith to engage the main access door locking structure and prevent unlocking thereof and to move said movable latching member to a position for engagement with one of the locking structure of the plug and access door upon movement of the switch actuating member to close the switch.

10. An electrical switch and receptacle unit comprising a casing, a receptacle within the casing, said casing having an access opening, said casing having a receptacle access door for said opening, said receptacle access door including spring means biasing the door to the closed position, a switch within the casing, a switch actuating member connected to the switch to open and close the switch, said switch actuating member including means for operation thereof exterior of the casing, a plug having locking structure thereon, said plug being receivable through the receptacle access opening and connectable to the receptacle with the locking structure of the plug positioned within the casing, a finger on the interior face of the access door, said finger projecting into the casing when the door is closed, a latching plate slidably mounted within the casing, said latching plate being slidable to a position partially blocking the receptacle access door, said latching plate having a recess' on one edge thereof for engagement of the plate with the locking structure of the plug, said latching plate having an opening therein separate form the recess for the passage of said finger when the door is closed, a latching element pivotally mounted on the interior surface of the latching plate in alignment with said opening, said latching element being larger than the opening to prevent pivoting thereof outwardly of the receptacle casing, said'finger having a detent thereon to engage the latching element when the door is closed and the latching plate is 'positioned to partially block the receptacle access opening to thus prevent opening of the door, and linkage within the casing between the latching plate and switch actuating member to slide the latching plate to a position partially blocking the receptacle access opening upon movement of the switch actuating member to close the switch.

References Cited by the Examiner UNITED STATES PATENTS 2,439,708 4/1948 Abraham 20050.1

FOREIGN PATENTS I 15,427 1915 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

M. GINSBURG, Assistant Examiner. 

3. AN ELECTRICAL SWITCH AND RECEPTACLE UNIT COMPRISING A CASING, A RECEPTACLE WITHIN THE CASING, SAID CASING HAVING A RECEPTACLE ACCESS OPENING, SAID CASING HAVING A RECEPTACLE ACCESS DOOR FOR SAID OPENING, A SWITCH WITHIN THE CASING, A SWITCH ACTUATING MEMBER CONNECTED TO THE SWITCH TO OPEN AND CLOSE THE SWITCH, SAID SWITCH ACTUATING MEMBER INCLUDING MEANS FOR OPERATION THEREOF EXTERIOR OF THE CASING, AND AN INTERLOCK STRUCTURE WITHIN THE CASING OPERATIVELY CONNECTED TO THE SWITCH ACTUATING MEMBER TO LOCK ONE OF A PLUG CONNECTED TO THE RECEPTACLE AND THE CLOSED RECEPTACLE ACCESS DOOR IN PLACE WHEN THE SWITCH ACTUATING MEMBER IS POSITIONED TO CLOSE THE SWITCH. 